Æthelfrith

He became the first Bernician king to also rule the neighboring land of Deira, giving him an important place in the development and the unification of the later kingdom of Northumbria.

[1] The 20th-century historian Frank Stenton wrote that "the continuous history of Northumbria, and indeed of England, begins with the reign of Æthelfrith", and that "he was the real founder of the historic Northumbrian kingdom, and he was remembered as the first great leader who had arisen among the northern Angles.

For he conquered more territories from the Britons, either making them tributary, or driving the inhabitants clean out, and planting English in their places, than any other king or tribune.

[5] Áedán mac Gabráin, the king of Dál Riata (to the northwest of Bernicia), was alarmed by Æthelfrith's successes, and in 603 he led "an immense and mighty army" against him.

[22] It has been suggested that Æthelfrith may have done this for tactical reasons, to catch the Britons by surprise and force them to change their plans in order to protect the monks.

[23] Æthelfrith's victory at Chester has been seen as having great strategic importance, as it may have resulted in the separation of the Britons between those in Wales and those to the north; however, Stenton noted that Bede was mainly concerned with the massacre of the monks and does not indicate that he regarded the battle as a historical "turning-point".

[24] John T. Koch says that the older view that the battle cut the two British areas off from each other is now "generally understood" to be outdated, as Æthelfrith died soon after, and there is "almost no archaeological evidence for Anglo-Saxon settlement within the pagan period in Cheshire or Lancashire", and in any case the sea would have been the primary means of communication.

Æthelfrith sent messengers to bribe Rædwald with "a great sum of money" into killing Edwin; Bede reports that his first message had no effect, but Æthelfrith sent more messengers and threatened war if Rædwald did not comply (bribes and threats of this kind may have previously been used to accomplish Hereric's killing[11]).

Rædwald eventually agreed to kill Edwin or hand him over to Æthelfrith's messengers, but was reportedly dissuaded from this by his wife, who said that such a thing was unworthy of his honour.

[27] While presented by Bede as being fought simply over the issue of Edwin, this war may have actually involved questions of power and territory between the two rulers.